. >> reporter: bret's family enjoyed their vacation getaway. most flew for free. >> i used about tension trip trips with my miles. fantastic. >> the value of frequent fliers miles is falling. they crunched the numbers and found it is a waste on certain flights. >> it is only worth it to use it on flights that cost $300 or more. >> reporter: fortunately taking a trip with frequent flier miles is a challenge. according to web fly.com, travelers are most likely to are have success with southwest airlines, followed by u.s. airways at 67%. but to get the flight you want, book early and be flexible with your travel dates. if you don't have enough miles to travel, most allow family and friends to transfer to one another. but that can be costly, too. so check the airlines rules and what happens to your miles if the airline goes bankrupt. >> if it is a major carrier your frequent flier program will be bout by another airline and you won't lose your miles. >> for bret a widely used frequent account is a great thtoannoand wusa9.com. >>> and here's another